1. Field of the Invention
The present invention relates to an evaluation device for a control unit such as an electronic control unit (hereinafter referred to as an “ECU”) of a vehicle, in particular an evaluation device provided with a common communication line with a plurality of control units and evaluating control units communicating with each other.
2. Description of the Related Art
Automobiles carry engine control ECU's for electronic control of their engines. An engine control ECU is sent signals indicating the engine speed, vehicle speed, etc. as detected by sensors provided on the chassis. The engine control ECU performs predetermined processing based on the received signals, sends the results of processing (for example, the fuel injection amount, ignition timing, etc.) converted to electrical signals to actuators and other control mechanisms provided in the vehicle, and controls the amount of injection of fuel, controls the ignition timing, controls knocking, controls the idling speed, etc. in a comprehensive fashion.
The signals input to an engine control ECU and the signals output from an engine control ECU change instant to instant. Further, these signals include signals which change according to each other such as signals indicating the engine speed, vehicle speed, etc. and control signals. Therefore, when confirming the operation of an engine control ECU or evaluating performance, it is necessary to mount the engine control ECU on an actual vehicle or use a simulator simulating the behavior of a vehicle.
Realization of such a simulator requires a program simulating vehicle behavior. Such a program is constructed based on the dimensions of the vehicle (for example, displacement, tire size, etc.) and includes as input elements the state in which the vehicle is placed, for example, the air temperature and atmospheric pressure, the vehicle weight, the road gradient, etc. and the current input states, for example, the degree of depression of the accelerator pedal, the degree of braking, and other human operational input, output of the ECU given to the vehicle, and other current input states. In a vehicle model, it is necessary to change the output of the program expressing vehicle behavior instant to instant in accordance with the changes in these input elements. A program simulating and reproducing such vehicle behavior is called a “vehicle model” (for example, see Japanese Unexamined Patent Publication (Kokai) No. 11-326135).
FIG. 6 shows an example of an evaluation device for an engine control ECU of the related art using a vehicle model. The vehicle model 40 is constructed based on dimensions of the set model such as the displacement and tire size. It receives the ignition signal or fuel injection amounts from the ECU 1 or the throttle opening degree etc. input from an input means 31 through an interface 32. Based on these inputs, the device simulates the states of the different parts of the vehicle such as the engine speed and vehicle speed and transmits the results of processing through the interface 33 to the ECU 1.
The vehicle model 40 is comprised of an air processor 41 for processing the intake pressure, intake air flow, etc., a torque processor 42 for processing the torque or knock, an A/F processor 43 for processing the air-fuel ratio, a speed processor 44 for processing the engine speed or vehicle speed, etc. The functions of the parts are realized by a software program.
On the other hand, recent vehicles carry a plurality of ECU's. As shown in FIG. 7, the plurality of ECU's, for example, an engine control ECU 1, a body ECU 2, an automatic transmission (AT) control ECU 3, an airbag ECU 4, etc. are connected via a bus 5 and construct a local area network (hereinafter referred to as a “vehicle-mounted LAN”). These ECU's can communicate data with each other. There are various communication standards for vehicle-mounted LAN's. The leading ones are the IEEE 1394, CAN, Lin, X-by-Wire, etc.
Each of the plurality of ECU's performs control based on the values of sensors or the operating state of the equipment in the vehicle. For example, the engine control ECU 1, as explained above, controls the fuel injection amounts etc., while the body ECU 2 controls the lamps, doors, etc.
Each ECU mounted in the vehicle controls the object assigned to it alone, but sometimes requires the transfer of data with other ECU's. The ECU's can utilize the vehicle-mounted LAN for the transfer of data with other ECU's and thereby cooperatively control the system. For example, if the engine control ECU 1 receives an airbag failure signal from the airbag ECU 4, the engine control ECU 1 can enter a failsafe mode where it limits the speed to under a certain constant speed or perform other operations.
When developing one such ECU alone in a state with no actual vehicle on hand, it is necessary to connect this ECU to an evaluation device provided with a simulator able to produce the communication signals generated by other ECU's for evaluation and study. For example, when CAN is adopted as the communication standard of the vehicle-mounted LAN, the evaluation device has to function to transfer signals according to the CAN standard. Further, sometimes it is required that an acknowledgement signal indicating that the signal has been received be sent to that device in the method of communication. In such a case, when testing an ECU, it is necessary that the evaluation device send such an acknowledgement signal.
FIG. 8 shows an ECU evaluation device of the related art provided with a signal transfer function based on this communication standard. This is comprised of a simulator 10 and a personal computer (hereinafter referred to as a “PC”) 50 connected to this simulator 10. The PC 50 is comprised of a central processing unit (CPU) 51, a display 52 such as a cathode ray tube (CRT) or a liquid crystal display (LCD), and an input unit 53 such as a keyboard or mouse. By using an input unit 53, it is possible to give to the simulator 10 the state in which the vehicle is placed (for example, the air temperature, atmospheric pressure, vehicle weight, road gradient, etc.), the degree of depression of the accelerator pedal, the degree of braking, and other operations of the driver. Note that as shown in the figure, the simulator 10 may have a display 61 and input unit 62 connected to it. Further, it is also possible not to connect to a PC 50 and use another display 61 and another input unit 62 instead of the display 52 and input unit 53.
On the other hand, the simulator 10 is comprised of a communication board 11, an input/output board 12, and other boards and a CPU 13. The transfer of signals between the boards and PC 50 and the transfer of signals between boards are handled through the CPU 13. These boards are comprised of CPU's and ROM's, RAM's, and other memories. The functions of these boards are realized by a software program.
The CPU 13 performs for example the processing of the vehicle model. It receives signals from the ECU 1 through the communication board 11 and input/output board 12, simulates the states of the different parts of the vehicle such as the engine speed, vehicle speed, etc., and sends the results of processing to the ECU 1 through the communication board 11 and input/output board 12. Further, it sends them to the PC 50 for display of the states on the display 52 of the PC 50.
The input/output board 12 is a board simulating the signal of an actual vehicle speed sensor from the pattern of the change in the vehicle speed input from the input unit 53 of the PC 50 and outputting a simulated signal. The pattern of change of the vehicle speed from the PC 50 is received by the input/output board 12 through the CPU 13 and output to the ECU 1. Alternatively, the vehicle speed value of the vehicle model processed at the CPU 13 is received by the input/output board 12 and output to the ECU 1. The input/output board 12 receives for example an ignition signal from the ECU 1, converts that signal to a digital amount, and sends it to the CPU 13. Further, it sends it to the PC 50 through the CPU 13 to display the state of the ignition signal at the display 52.
On the other hand, the communication board 11 has the function of preparing an acknowledgement signal when receiving a signal from the ECU 1 or transmitting a signal input from the input unit 53 of the PC 50 to the ECU 1. FIG. 9 is a block diagram of the functions of a communication board 11 of the related art. As shown in the figure, this is comprised of a monitor data converter 21, an acknowledgement signal generator 22 using communication logic, a transmission signal generator 23 using communication logic, and a communication protocol converter 24. The functions of these parts, as explained above, are executed by a software program by the CPU, ROM, RAM, etc.
For example, when an engine speed signal is transmitted from the ECU 1 to the communication board 11, the transmitted engine speed signal is converted to viewable data by the monitor data converter 21, is transmitted to the PC 50, and is displayed at the display 52. Next, the acknowledgement signal generator 22 responds to the transmitted signal and generates an acknowledgement signal based on the communication standard indicating receipt of the signal. This acknowledgement signal is transmitted through the communication protocol converter 24 to the ECU 1. On the other hand, for example, when desiring to transmit a signal indicating that the airbag is normal to the ECU 1, if the normal state of the airbag is input from the input unit 53 of the PC 50, in response to this signal, the transmitted signal generator 23 generates a transmission signal based on the communication standard and transmits this signal to the ECU 1 through the communication protocol converter 24.
As explained above, when a plurality of ECU's share a single communication line to communicate among each other so as to share information for use, when developing any of these ECU's alone in a state with no actual vehicle on hand, the above evaluation device becomes necessary. In actuality, however, the time required for starting up each ECU differs. Therefore, the state of ECU communication right after the power is turned on becomes unstable. Accordingly, in an actual vehicle, for example when the already started up ECU (A) transmits a signal to a not started up ECU (B), the ECU (B) does not return a signal indicating the receipt of the signal from the ECU (A) to the ECU (A). Therefore, the ECU (A) may erroneously judge that the ECU (B) has broken down or the ECU (A) may continue sending the signal to the ECU (B) and cause an abnormality on the communication line. In the evaluation device of the related art, there was the problem that since the communication boards are always operating normally during the evaluation of the ECU's, it is not possible to simulate the behavior of the ECU's under such unstable states right after the power is turned on.